Boulenger's Keelback

The body of F. asperrima is short and cylindrical, and has a clear neck and slightly pointed head. The eyes have rounded pupils, and the nostrils are narrow, directed slightly upwards. The tail is long. At hatching, it is 10 cm (3.9 in) long and grows to an adult length of 40–70 cm (16–28 in). The female is longer.

F. asperrima is found in Sri Lanka, in both dry and wet climatic zones up to 1,000 m (3,300 ft) above mean sea level. It is abundant in waterways, such as flooded rice fields, ponds, lakes, marshes, rivers and streams.

F. asperrima is oviparous, diurnal and nocturnal. In dry conditions during the summer, it undergoes aestivation. It is active in water bodies in search of its prey, which consist mainly of fishes and frogs. It is known to be very aggressive. When threatened, it attempts to bite, by flattening its head and neck as does the cobra. The bite may cause wounds. Also, it may release a noxious odor.

The common name "Boulenger's keelback" is in honour of Belgian-born British herpetologist George Albert Boulenger.